Building A Big-Block Ford Using Shelf Parts - Ah Rats!

If this catches on, it won't be long before big-block Fords start showing up between the framerails of Chevelles and Camaros. In fact, it seems inevitable. When it's possible to crack 775 hp with a pump gas 532ci Ford using plebian off-the-shelf components for $9,600, Bow Tie brand loyalty seems like a sure-fire way to cross the finish line second. This isn't some bench racing exercise in bogus budgets and theoretical power figures, either. The aforementioned numbers are real, and we just did it. So scrutinize the parts list in fervent disbelief if you please. It's all there, every last nut, bolt, gasket, bearing, and freeze plug. Although it's premature to declare a new bang-for-the-buck engine platform champ after just one buildup, it's clear that Rat motors are falling behind on their mortgage payments, and big-block Fords are ready to seize the underhood real estate they once called home.

Granted, it's unsportsmanlike to gloat, but a ratio of $12 per hp at this power level is quite an accomplishment. After all, building a 500hp small-block Chevy-arguably the most economical of all engine platforms-for $6,000 would be pretty darn tough to pull off. That said, we can't take any of the credit. What accounts for this staggering performance value is a set of killer 400cfm cylinder heads from Jon Kaase Racing Engines, a dirt-cheap Scat rotating assembly, the skilled craftsman at the School of Automotive Machinists (SAM), and the dimensionally generous architecture of the 385-series Ford big-block. Throw all these factors together, and the result is serious power and cubic inches in a seriously affordable and easy-to-assemble package.

Can You Say Cubes?
Whether it was a stroke of genius or a convenient coincidence, Ford engineers unleashed an engine design quite accommodating of massive cubic inches with the introduction of the 429/460 385-series big-block in 1968. Compared to the FE family of engines it was intended to replace, the new big-block featured a larger 4.900-inch bore spacing, thicker cylinder walls, a taller 10.320-inch deck height, a capacious "skirtless" crankcase, and a camshaft positioned way up high in the block. With today's endless selection of long-armed aftermarket crankshafts, 429/460 Fords can easily be built as large as 557ci with production blocks and off-the-shelf components. Comparatively handicapped by a shorter 9.800-inch deck height and smaller 4.840-inch bore spacing, the ubiquitous big-block Chevy is limited to about 496 ci. Anything larger requires stepping up from a production 454 block to either an aftermarket or a GMPP Siamesed-bore 502 block. Either of those options will set you back $2,000 to $3,000, as opposed to $50 for a seasoned production 460 Ford block out of a salvage yard. And since the 429/460 was manufactured for nearly 30 years, there's an abundance of cheap cores.

Singing the virtues of easy displacement on paper is a far cry from actually assembling a motor, but fortunately, big-inch Fords go together as easily as their specs suggest. Despite the fact that stock 460s used a relatively short 3.850-inch stroke, their blocks effortlessly swallow up much longer-armed cranks. "This 532 was a piece of cake to put together. The 4.300-inch crank we used dropped right in, and we didn't have to grind the block at all for rod clearance," says Judson Massingill of SAM. "There's just a ton of room between the oil pan rails. In fact, to fit a 4.500-inch crank in these motors you barely have to notch the bottom of each cylinder. With a big-block Chevy, it takes a lot more grinding just to fit a 4.250-inch crank."

Short-Block
If there's any truth to readers' letters, the Chevy bias in the hot rodding media is like liberal bias in the mainstream media. No one wants to admit it, but there's sufficient evidence that it exists. That being the case, as big-block Ford protgs in need of a mentor, the best man for the job was Jon Kaase. Although he's best known for winning three Jeg's Engine Masters Challenge competitions and powering the last 12 IHRA Pro Stock champions to victory, Kaase is a self-confessed 460 nut. He started tinkering with the big Ford during the '70s, while working on Don Nicholson's NHRA Pro Stock team, and has been picking up where the factory left off ever since. His guidance was essential in sorting out the specs on our combination.

The simple goal of this buildup was to produce enough power to push a typical street car deep into the 9s, while still maintaining enough streetability to make an occasional trip down to the Piggly Wiggly. The first order of business was sorting out the ideal bore and stroke dimensions. At 4.360 inches from the factory, a standard-bore 429/460 block offers plenty of deep-breathing potential as-is. "If you're trying to build a 1,000hp race motor, then your best bet is a 4.600-inch bore with an aftermarket block. However, there's really no need to bore a block more than 0.030 over on a street motor, although most production blocks have enough wall thickness to safely handle an 0.080-over bore," Kaase explains. Upon scoring a local block off of eBay that had already been rebuilt once, we decided to punch it out to 0.080-over after sonic checking revealed plenty of meat remaining between the bores.

To keep costs at a minimum, we opted for a Scat 4.300-inch cast-steel crankshaft, which is also offered in 4.150- and 4.500-inch configurations. Combined with a 4.440-inch bore diameter, it netted a total of 532 ci. We're not ones to challenge the notion of irreplaceable displacement, but there's certainly a point of diminishing returns. "For a street/strip build like this, I prefer a 4.300-inch stroke," Kaase opines. "As you go bigger in cubic inches with a 4.500-inch crank, you might pick up more torque through the midrange, but the difference in high-rpm power will be negligible." With the bore and stroke dimensions finalized, the rotating assembly was finished off with a set of Scat 6.700-inch steel rods, and Probe 10.9:1 pistons. Scat's kit also includes rings, bearings, a flexplate, and a balancer all under one convenient part number (1-94955BE) for $1,495.

P-51 Cylinder Heads
While the budget Scat rotating assembly and the 429/460's commodious dimensions make it possible to build an economical big-inch short-block, the real trick in making loads of power is a set of killer cylinder heads. Flowing an astonishing 401 cfm through 310cc intake ports right out of the box, Kaase's CNC-ported P-51 heads definitely fit that description. Perhaps even more impressive are the heads' mid-lift flow numbers, which hit 330 cfm by 0.400-inch lift and 375 cfm by 0.500-inch lift. "These heads come pretty close to 400 cfm by 0.550 lift, and I don't think there are another set of heads out there that can match that," says Kaase. Performance like that usually carries a hefty price tag, but the P-51s can be had in fully assembled trim for a ridiculously cheap $2,450. That includes stainless steel 2.25/1.76-inch valves, Manley valvesprings good for 0.800-inch lift, custom guideplates, ARP rocker studs, and Comp Cams retainers and locks.

Interestingly, what makes these heads so good is a combination of engineering genius, and failures in the original Ford design. Borrowing architectural cues from the small-block Cleveland, Ford engineers incorporated large ports and canted valves into the 429/460 cylinder heads. With flat 15-degree valve angles, the design seemed like a winner on paper, but in reality, its performance fell far short of its promise. This, combined with the abrupt end of the muscle car era, is why 460s were installed primarily in trucks and large sedans over the years, and developed an unfavorable reputation. "The factory big-block Cobra Jet heads were a pretty good design with some fundamental design flaws. The chambers were offset too far to the outer edges of the block, so half of it was positioned outside of the block and the other half was essentially a big quench pad," Kaase explains. "As a result, the intake valve got very close to the outside of the block as it opened, which caused severe shrouding and impaired flow. When I redesigned the heads for Ford Racing in 2001, I moved the entire combustion chamber closer to the intake manifold and centrally positioned the intake valves, setting them up at an 8.5-degree angle. The new valve location significantly improves flow at low- and mid-lift."

In as-cast form, Ford Racing's Super Cobra Jet heads are capable of flowing 345 cfm, but Kaase has been able to coax over 400 cfm out of them with some skilled port work. This led to the advent of the P-51 castings, which provide comparable airflow to a set of fully ported Super Cobra Jet's in an as-cast design for the ultimate in out-of-the-box performance. "In addition to casting ports that mimicked the design of a set of fully ported SCJ heads, we revised the water jacket to allow more aggressive porting of the short-turn radius. Likewise, we reshaped the combustion chambers and touched up the bowls and the area beneath both valve seats before writing a CNC program to accurately replicate it," says Kaase. "None of this stuff is new, and we integrated design elements from various cylinder heads we've worked on-like the Yates and Cleveland heads-and incorporated them into the P-51s. One of the biggest challenges was keeping the ports in the stock locations. Raising them would have picked up flow quite a bit, but if your heads won't work with the off-the-shelf intake manifolds and headers that are out there, you're shooting yourself in the foot."

Showtime
During the early stages of this project, Kaase enticed us with a proposition that seemed too good to be true: "With a set of P-51 heads and one of my custom cams, you'll make close to 800 hp." It turns out he was right. Our 532 belted out 775 hp at 6,500 rpm, and 673 lb-ft at 5,300 rpm on 93-octane pump gas. It's worth noting, however, that from a standpoint of typical magazine testing protocol, we missed the mark. In other words, we set our combination up to most accurately replicate its operating environment inside a car-like most readers would-instead of implementing some common tricks for the sole purpose of posting a big dyno number. The Hooker headers, for instance, are the exact same set of pipes we'll be running in the '93 Mustang this 532 will ultimately power. Most dyno headers don't have nearly as many bends and kinks, which can only impede flow. "On a 750hp motor, a dyno header-or a chassis header as many people call them-can easily be worth 20-25 hp compared to a production-car-style header of the exact same diameter," explains Judson. "The bends of a production header can sometimes improve low-end torque, but they'll definitely hurt the top end, especially at this power level." Furthermore, we opted for an Edelbrock water pump due to its excellent flow characteristics, and the bulletproof reliability of a mechanical pump on a street/strip motor even though an electric unit would have freed up some more ponies. The bottom line is that if dyno racing is your goal, you can certainly improve upon our build with a few simple tricks. In the meantime, we're more than content with our real-world 775 hp.

Will It Hold?
With the potential to effortlessly make such prodigious power with a big-block Ford, durability becomes a major concern. And let's face it, the big-block's smaller brethren-whether 302s or 351 Windsors-are infamous for literally splitting their blocks in half under strenuous power loads. Rest assured, big brother is more than up to the task. "You can get up to 800 hp real quick with one of these motors with nice parts and no porting. Fortunately, Ford cast the 429/460 blocks using very strong metal," Kaase explains. "We have a production-block-based 521 dyno mule in the shop that has a Scat cast crank and steel rods that's making 900 hp. Just about everything we R&D has been tested on this motor. Despite the fact that we've done nothing at all to beef up the block and it has two-bolt mains, it's still holding together after thousands of dyno pulls.